Imagewise exposing a metal halide layer with laser to form permanent metal image

ABSTRACT

A RECORDING PROCESS WHICH COMPRISES IMAGEWISE EXPOSING A CRYSTAL LAYER OF METAL HALIDES TO AN ENERGY HAVING AN INTENSITY WHICH SATISFIES THE EQUATION   D=KIN   IN WHICH D IS THE OPTICAL DENSITY, K IS A CONSTANT EQUAL TO 6X10**-5, I IS THE INTENSITY OF THE EXPOSING ENERGY, AND N IS NUMBER OF 1 OR GREATER IS DISCLOSED.

IMAGEWISE EXPOSINC A METAL HALIDE LAYER WITH LASER TO FORM PERMANENT METAL IMAGE Filed June 9, 1972 IMAGE DENSITY o o HUI 0.0%

IMAGE DENSITY 0.02 Q Q o o o ENERGY (mJ) United States Patent Office 3,834,903 Patented Sept. 10, 1974 US. CI. 96-27 E 6 Claims ABSTRACT OF THE DISCLOSURE A recording process whrich comprises imagewise exposlng a crystal layer of metal halides to an energy having an intensity which satisfies the equation in which D is the optical density, K is a constant equal to 6x10 I is the intensity of the exposing energy, and n is a number of 1 or greater is disclosed.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording process. More particularly, the present invention relates to a process for forming permanent images by only exposing metal halides to light without conducting a chemical treatment.

2. Description of the Prior Art Hitherto, formation of images has been practiced by processes which comprise exposing photosensitive materials such as a silver halide emulsion or a diazophotosensitive composition to light, developing and fixing. In particular, the process in which silver halide emulsions are used is an excellent recording process and produces images having a high sensitivity and a high resolving power.

However, in the prior recording processes, images can not be obtained if chemical or physical treatment is not conducted. Furthermore, the recording element must be treated in the dark until the images are formed, because the recording element is subject to sensitizing by visible rays and rays having a wave length near the visible rays.

Recording processes which are quite different from the above processes have been proposed. For example, M. R. Tubbs introduced a recording process utilizing a film material composed of metal halide compounds or chalcogen compounds in The Journal of Photographic Sciences, Vol. 17, pages 162-169 (1969).

In the above-mentioned report, the disclosure is that images having a high resolving power can be obtained when visible rays of less than 5200 A. or ultraviolet rays are applied to a deposited lead iodide film at 160 to 220 C., because the exposed part changes its color from a yellowish orange to colorless, and that images having a resolving power above 1 micron can be obtained when exposing a metallic silver film and a lead iodide film laid on a glass support to light of 1 I./cm. at a room temperature; however the images deteriorate if they are not covered with a covering film.

As the result of many studies on processes for recording images in the light without conducting a chemical or physical treatment, the present inventors have found a resolving power above 1 micron can be obtained when above-described processes.

Therefore, an object of the present invention is to provide a new recording process. A second object of the present invention is to provide a recording process for forming images using only exposure without subsequent chemical or physical treatment. A third object of the present invention is to provide a recording process which can be conducted in the light. A fourth object of the present invention is to provide a recording process for forming images having a high contrast. A further object of the present invention is to provide a recording process by which multiple recording can be carried out.

SUMMARY OF THE INVENTION As the result of various studies so as to attain the above-described objects, the present inventors have found that metal halides are subjected to sensitizing semipermanently by excitation at a light intensity of below a threshold value, but form permanent images by excitation at a light intensity of the above-described value.

Namely, it has been found the metal halides have a characteristic satisfying the following equation:

wherein D is the optical density, K is a constant 6X10- I is the intensity of exposure, i.e., energy per area unit square (e.g. mL/cm?) is a number, generally 1 n 2.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS FIG. 1 and FIG. 2 are graphs which show the relation between the density of images obtained by the recording process of this invention and the energy applied.

DETAILED DESCRIPTION OF THE INVENTION The relationship set forth above shows a phenomenon not observed in common photosensitive materials.

The most important feature of the phenomenon found by the present inventors is that the density stays at zero even though energy is applied until the energy reaches a specific level and image density appears when the energy reaches a threshold value. Accordingly, the slope of the curve represented by D=KI (n 1) is large. This feature results in an excellent elfect on the process of the present invention.

The metal halides used in the process of the present invention include lead iodide, lead chloride, lead bromide, silver iodide, silver bromide, copper iodide, copper bromide and mercury iodide, which are used as single crystals, multi-crystals, mixed crystals, or as a deposited film or dispersed layer on a support.

As the metal of the metal halides, those having many electrons are preferable. The most preferable metal halides include those of lead and mercury. They are selected according to the objective, since the sensitizing energy intensity increases in order of the metal iodides, metal bromides and metal chlorides, the preferred metal halides being metal iodides.

As the energy source used for image formation, any energy source can be used so long as the electromagnetic wave has the light intensity range necessary to cause the non-linear phenomenon on the substances. For example, lasers such as a ruby laser (wave length: 6943 A.) can be used. For example, although a dispersion film of a lead iodide powder has no absorption in a wave length range longer than 52 me, it forms black images when exposed imagewise to a Giant Pulse ruby laser light of peak power max: 30 w. (half width: 15 n-sec.) at a room temperature. Since the metal halides have a specific absorption wave length respectively, it is preferable to apply light having a wave length longer than the specific absorption wave length. The dispersion film of the metal halides can be formed on a support such as glass, metals and plastic films using conventional techniques. The dispersion layer can be prepared by dispersing a metal halide in an aqueous solution of the common binder such as gelatin, polyvinyl alcohol, polystyrene and polyvinyl fluoride. The amount of the metal halide in the dispersion layer is not critical but is preferably about 1 mmole per 1 g. of the binder. The metal halide can also be used as low as 0.25 mmole per 1 g. of the binder.

In using the deposited film or dispersion layer as the recording element, it is preferable that the film or layer has a thickness greater 1 micron, preferably a thickness up to 100 micron.

According to the process of the present invention, since images having a high contrast and a high resolving power can be obtained by only applying energy having a specific value, it is possible to carry out multiple recording. For example, the multiple recording can be carried by concentrating the light in a multi-photon process by taking advantage of the non-linear eifect of the recording material to form images at various depths in the light sensitive layer. Further, the entire treatments until forming images can be carried out at room temperature in the light. Moreover, it has the advantage that pemanent images can be obtained without conducting treatments such as development, fixing and stabilizing.

Accordingly, the process of the present invention can be utilized for producing a copying mask and in many copying systems such as photo-resists, negative or positive films, microfilms and accumulation of information.

The present invention will be explained in greater detail by reference to the following examples.

Example 1 Lead iodide was dispersed in an aqueous solution of gelatin so as to have a concentration of 7.5 [1101/ g. gelatin. The solution was applied to a surface of a glass support and dried at room temperature under a reduced pressure to form a lead iodide layer of 40 1. in thickness.

When the resulting recording element was exposed imagewise to a Giant Pulse ruby laser (peak power max: 50 mW., half width: n-sec.), the exposed parts became black to produce a recording image.

The visible density of the exposed parts was determined using a Macbeth densitometer. The result obtained by plotting the relation between the energy and the density is shown in FIG. 1.

As is clear from the results shown in FIG. 1, a curve having a large slope, that is, image having a high contrast can be obtained for the first time using an energy of m].

Example 2 Images were formed in the same manner as described in Example 1 but a lead iodide layer of 20 was formed by dispersing a lead iodide powder in an aqueous solution of gelatin so as to have a concentration of 1.05 10- mol/g. gelatin, applying to a glass support and drying. The results obtained are shown in FIG. 2.

What is claimed is: i

l. A recording process which comprises imagewise exposing a crystal layer of metal halides to a laser energy source having an intensity sufiicient to form a permanent image without chemical treatment which intensity satisfies the equation in which D is the optical density, K is a constant equal to 6 10*, I is the intensity of the exposing energy, and n is a number greater than 1, wherein said metal halide is a member selected from the group consisting of lead iodide, lead chloride, lead bromide, silver iodide, silver bromide, copper iodide, copper bromide, mercury iodide and mixtures thereof.

2. The process of Claim 1, wherein said crystal layer is coated on a support.

3. The process of Claim 2, wherein said crystal layer is dispersed in a binder.

4. The process of Claim 3, wherein said binder is gelatin, polyvinyl alcohol, polystyrene or polyvinyl chloride.

5. The process of Claim 3, wherein the concentration of said metal halide is in excess of 0.25 mmole per g. of binder.

6. The process of Claim 1, wherein said crystal layer has a thickness between 1 and 100 microns.

References Cited M. R. Tubbs: High Resolution Image Recording on Photosensitive Halide Layers, The Journal of Photographic Science, vol. 17, 1969, pp. 162-169.

M. R. Tubbs, et al.: Photographic Applications of Lead Iodide, British Journal Applied Physics, vol. 15, 1964, pp. 1553-4558.

RONALD H. SMITH, Primary Examiner W. H. LOUIE, JR., Assistant Examiner US. Cl. X.R. 96-48 QP, R 

